Diffuser

ABSTRACT

A diffuser for attachment to an airflow outlet end of a hair dryer has an air inlet, a grille having a central portion and a plurality of air outlets for emitting a first part of the airflow; and a plurality of projections upstanding from the grille for contacting hair and emitting a second part of the airflow. The projections include a set of inner projections arranged about the central portion of the grille, and a set of outer projections arranged about the inner projections. The air outlets of a first subset of inner projections are arranged to emit air away from the central portion of the grille and the air outlets of a second subset of inner projections are arranged to emit air towards the central portion of the grille. The air outlets of the outer projections are arranged to emit air towards the central portion of the grille.

FIELD OF THE INVENTION

The present invention relates to a diffuser for a hair dryer.

BACKGROUND OF THE INVENTION

A diffuser is known form of attachment for a hair dryer. The diffuser is attached to the airflow outlet end of the hair dryer and serves to reduce the velocity of the airflow emitted from the hair dryer before it is incident upon the hair of the user.

A diffuser generally comprises a baffle and a grille connected to the baffle. The baffle has an air inlet end, an air outlet end which is larger than the air inlet end, and a tapering wall which extends between the air inlet end and the air outlet end. The air inlet end comprises an air inlet for receiving the airflow from the hair dryer. The wall of the baffle defines a diffusing air chamber within which the velocity of the airflow decreases as the cross-section of the air chamber increases. The grille is connected to the air outlet end of the diffuser and provides air outlets from which air is emitted from the diffuser. A set of projections or prongs are generally upstanding from the grille to contact the hair of the user during hair drying. Each of the projections generally has an air outlet for emitting air into the user's hair.

SUMMARY OF THE INVENTION

The present invention provides a diffuser for attachment to an airflow outlet end of a hair dryer, the diffuser comprising at least one air inlet for receiving an airflow from a hair dryer; a grille comprising a central portion and a plurality of air outlets for emitting a first part of the airflow from the diffuser; and a plurality of projections upstanding from the grille for contacting the hair of a user and for emitting a second part of the airflow; wherein the plurality of projections comprise a set of inner projections arranged about the central portion of the grille, and a set of outer projections arranged about the inner projections, and wherein the air outlets of a first subset of inner projections are arranged to emit air away from the central portion of the grille and the air outlets of a second subset of inner projections are arranged to emit air towards the central portion of the grille, and the air outlets of the outer projections are arranged to emit air towards the central portion of the grille.

Each of the projections preferably comprises an air inlet, an air outlet spaced from the air outlets of the grille, and a bore extending between the air inlet and the air outlet. Thus, a first part of the airflow which enters the diffuser through the air inlet(s) is emitted from the air outlets of the grille, whereas a second part of the airflow is emitted from the air outlets of the projections.

Each projection preferably comprises a single air outlet. Each air outlet may comprise a single aperture, or a plurality of apertures which emit air in a common direction (that is, towards or away from the central portion of the grille), and which together define the air outlet. For example, the air outlet may comprise a mesh, grille or other array of relatively small apertures which together define the air outlet. As another example, the air outlet may comprise a plurality of apertures spaced along the projection, for example along the length of the projection, and which emit respective portions of the air received by the projection in a common direction.

The longitudinal axes of the bores of the projections are preferably parallel to the longitudinal axis of the diffuser. The air inlet of each projection is located on an internal surface of the grille, and preferably has a size which is larger than that of each of the plurality of air outlets of the grille. For example, each projection preferably has an air inlet which is circular in shape, and has a diameter which is in the range from 3 to 15 mm.

The air outlet of each projection is preferably located in an end portion of the projection which is remote from an external surface of the grille. The air outlet is preferably located on a side surface of the projection so that each projection emits a respective part of the airflow in a direction which is angled to the longitudinal axis of the diffuser. Each projection preferably has an air outlet which has a size which is larger than that of each of the plurality of air outlets of the grille. Each projection has a tip which is remote from the grille and a length extending in a direction extending from the grille to the tip. Each projection is preferably substantially conical or frustoconical in shape, so as to taper inwardly in a direction extending towards the air outlet end. Each air outlet of the projections preferably has a generally elongate shape; in other words, the length of the air outlet is greater than the width of the air outlet.

In order to reduce the time required to dry hair using the diffuser, the air outlets of the projections are arranged to emit air in various directions. In a preferred embodiment, the projections are divided into inner projections and outer projections arranged about the inner projections. Preferably, the inner projections are arranged in an annular array. The inner projections are preferably arranged about some of the air outlets of the grille so that a portion of the second part of the airflow is emitted from those air outlets of the grille, following a flow path defined by the inner projections.

The number of projections in the first subset of inner projections is preferably equal to the number of projections in the second subset of inner projections. A combination of the first subset and the second subset preferably forms the entirety of the inner projections. The inner projections may be arranged at equal angular intervals forming an annular array with angularly equidistant projections. As such, for each projection, the flow disturbance caused by the neighbouring projections may be kept to minimum and equally distributed along the annular array.

Preferably, the first subset of inner projections and the second subset of inner projections are alternately arranged about the central portion of the grille, further improving the radially balanced distribution of air emitted by the inner projections towards and away from the central portion of the grille.

The air outlets of the first subset of inner projections may be arranged to emit air radially away from the central portion of the grille and the air outlets of the second subset of inner projections may be arranged to emit air radially towards the central portion of the grille. With such an arrangement of inner projections, a vortex effect for improving heat convection and flow distribution can be created.

Such an arrangement of inner projections can provide a balanced airflow velocity distribution proximate to the external surface of the grille by emitting air towards the centre of the diffuser as well as towards the outer periphery of the diffuser in substantially equal airflow rates. Accordingly, a more balanced airflow, without creating heat sinks or dead airflow regions adjacent to the external surface of the grille may be achieved. This is important for consistent heat treatment of hair without causing damage to the hair by excessive heat in certain regions of the diffuser surface when in use.

Preferably, the outer projections are arranged in a second annular array. The outer projections are preferably arranged at equiangular intervals. The outlets of the outer projections may be arranged to emit air radially towards the central portion of the grille, thus creating a vortex effect. The second annular array formed by the outer projections is preferably concentric with the first annular array formed by the inner projections. Furthermore, the angular spacing between adjacent outer projections is preferably substantially the same as the angular spacing between adjacent inner projections. The concentric and regular arrangement of first and second annular arrays further assist in creating and maintaining balanced airflow along the surface of the diffuser.

The plurality of projections may comprise a set of intermediary projections located between the inner projections and the outer projections. The intermediary projections may be arranged in a third annular array. Preferably, each of the intermediary projections comprises a single air outlet arranged to emit air towards the central portion of the grille. The air outlets of the intermediary projections may be arranged to emit air radially towards the central portion of the grille, thus creating a vortex effect.

Preferably, the intermediary projections are angularly offset relative to the inner projections and the outer projections. With this arrangement, the flow path of the air emitted from the intermediary projections may not be directly obstructed by the air emitted from the inner projections. Furthermore, the air flow in corridors defined by the air emitted from the inner and outer projections may be stimulated by the intermediary projections, providing further balance to the airflow and heat distribution along the surface of the diffuser.

The third annular array formed by the intermediary projections is preferably concentric with the second annular array formed by the outer projections and arranged within the area defined by the inner and outer projections. Preferably, the intermediary projections are located adjacent to the outer periphery of the diffuser, closer to the outer projections than to the inner projections.

In a preferred embodiment, the outer periphery of the diffuser defines a scalloped outer edge. Accordingly, the scalloped edge provides the diffuser an ergonomic handling ability when in use and an aesthetically pleasing look. Furthermore, the depressions formed by the scalloped design along the periphery of the diffuser may improve visibility of hair when the diffuser is in use.

The number of intermediary projections is preferably equal to the number of outer projections. Furthermore, the intermediary projections and outer projections may be alternately arranged about the central portion of the grille, at equal angular intervals. Such symmetrical arrangement may provide a further balanced airflow and heat distribution along the surface of the diffuser

The central portion of the grille is preferably circular and unperforated. Accordingly, the air is emitted through air outlets arranged around this circular and unperforated area. The unperforated central portion of the diffuser may act as an obstacle to stop the airflow from directly exiting the diffuser along the same axis as it enters the diffuser.

Accordingly, regions of increased airflow proximate to the central portion of the diffuser may be inhibited through a controlled direction of the airflow throughout the entirety of the diffuser.

The diffuser preferably comprises a second unperforated area between the inner set of projections and the outer set of projections. The second unperforated area is preferably annular and concentric with the central portion of the grille. The second unperforated area may comprise an inner rim and an outer rim, wherein the outer rim is embossed with respect to the inner rim, creating a raised outer peripheral area, with respect to the central portion. Preferably, the raised outer peripheral area provides a base for the outer and intermediary projections.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a left side, front perspective view, from above, of a diffuser;

FIG. 2 is a right side, rear perspective view, from above, of the diffuser;

FIG. 3 is a top view of the diffuser;

FIG. 4 is a side view of the diffuser;

FIG. 5 is a bottom view of the diffuser;

FIG. 6 is a left side, front exploded view of the diffuser;

FIG. 7 is a right side, rear exploded view of the diffuser;

FIG. 8 a is a side sectional view taken along line A-A in FIG. 3 ;

FIG. 8 b is a side sectional view taken along line B-B in FIG. 3 ; and

FIG. 9 is a left side, front perspective view, from above, of an example of a hair dryer to which the diffuser may be connected.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 5 are external views of a diffuser 10. The diffuser comprises an air inlet 12 for receiving an airflow from an airflow outlet end of a hair dryer. With reference also to FIGS. 6 and 7 , the air inlet 12 is generally annular in shape, and is in the form of an aperture located at the air inlet end 14 of baffle 16. The baffle 16 has an air outlet end 18 which is larger than the air inlet end 14, and an outwardly tapering wall 20 extending between the air inlet end 14 and the air outlet end 18. As illustrated in FIGS. 8 a and 8 b , the tapering wall 20 of the baffle 16 defines a diffusing air chamber 22 through which the airflow passes within the diffuser 10.

The baffle 16 comprises an annular inlet channel 24 for receiving airflow from the air inlet 12, and from which the airflow is emitted into the air chamber 22. The air inlet channel 24 is defined by an annular inner wall 26 and arranged to emit air along the central longitudinal axis C of the diffuser 10 as illustrated in FIG. 4 , directly towards the air channel 22. The air chamber 22 is further defined by an airflow dampener 28.

A grille 30 is connected to the air outlet end 18 of the baffle 16. The grille 30 is generally concave in shape. The grille 30 comprises air outlets from which a first part of airflow is emitted from the diffuser 10. These air outlets comprise a first array of air outlets 32 which are located in a central annular region of the grille 30, and a second array of air outlets 34 which are located in a peripheral region of the grille 30 which extends around the first array of air outlets 32. The air outlets 32, 34 have the same size and shape. Each of the air outlets 32, 34 is circular in cross-section. Each of the air outlets 32, 34 may be cylindrical in shape, but in this embodiment each of the air outlets 32, 34 is frustoconical in shape, tapering inwardly from the internal surface of the grille 30 towards the external surface of the grille 30. At the external surface, each of the air outlets 32, 34 has a diameter which is in the range from 0.5 to 2.5 mm, and in this embodiment is in the range from 1.5 to 1.6 mm Each of the air outlets 32, 34 has a perimeter defined by the external surface of the grille 30 which is sharper than the perimeter defined by the internal surface of the grille 30. The perimeter of the air outlets on the internal surface of the grille 30 is preferably rounded, and has a curvature with a radius in the range from 0.2 to 0.4 mm.

Within each array, the air outlets 32, 34 are regularly spaced. The spacing between neighbouring air outlets is in the range from 0.5 to 2 mm, and in this embodiment is also in the range from 1.5 to 1.6 mm.

With particular reference to FIG. 3 , the first array of air outlets 32 is arranged in a first annular array which extends around a central portion 36 of the external surface of the grille 30, and which receives airflow emitted from the annular inlet channel 24, along axis C through the central portion of the air chamber 22. The second array of air outlets 34 is arranged in a second annular array which surrounds, and is concentric with, the first array of air outlets 32. The second set of air outlets 34 generally receives airflow emitted from the annular inlet channel 24, through the peripheral portion of the air chamber 22.

With reference to FIGS. 3 and 8 a, central portion 36 of the grille 30 defined by a circular periphery 38 between the longitudinal axis C and the first array of air outlets 32 is devoid of air outlets 32, 34 or projections 60, 62, 64 and 66. An annular region 40 of the grille 30, which is located between the arrays of air outlets 32, 34, is devoid of air outlets of the grille 30. The annular region 40 is bounded by an inner rim 42 and an outer rim 44. The outer rim 44 is embossed with respect to the inner rim 42. Accordingly, a raised outer peripheral area 46 is defined between the outer rim 44 and an external periphery 48 of the grille 30 The surface of the annular region 40 is generally curved between the inner rim 42 and the outer rim 44 but this is not essential. For example, the external surface of the annular region 40 may be otherwise profiled or generally flat.

The diffuser 10 also comprises a plurality of projections for contacting the hair of a user, and for emitting a second part of the airflow from the diffuser 10. The projections are upstanding from the external surface of the grille 30. In this embodiment, the projections comprise a set of inner projections 60, 62 a set of outer projections 64 and a set of intermediary projections 66. In this embodiment, the set of outer projections 64 and the set of intermediary projections 66 have the same size and shape. But alternatively, the projections may have different sizes. For example, the set of inner projections 60, 62 may be smaller than the set of outer projections 64 or the set of intermediary projections 66.

The set of inner projections 60, 62 are arranged in an annular array in the central portion 36 of the grille 30. In this embodiment, the set of inner projections 60, 62 comprises ten projections which are equally angularly spaced about the longitudinal axis A.

The set of inner projections 60, 62 comprises a first subset of inner projections 60 and a second subset of inner projections 62. Each of the first subset of inner projections 60 comprises an air inlet 68 formed in the grille 30, an air outlet 70 and a bore 72. Similarly, each of the second subset of inner projections 62 comprises an air inlet 74 formed in the grille 30, an air outlet 76 and a bore 78. The air inlets 68, 74 are circular in shape, and have a diameter which is greater than the diameter of the air outlets 32, 34 of the grille 30. The air outlets 70, 76 are in the form of an elongate side air outlet, which has a height which is approximately one half of the height of the projections 60, 62, and a width which is smaller than the height of the air outlets 70, 76 of the projections 60, 62. The air outlets 70 of the first subset of inner projections 60 are arranged to emit air away from the central portion 36 of the grille 30, whereas the air outlets 76 of the second subset of inner projections 62 are arranged to emit air towards the central portion 36 of the grille 30. In this embodiment, the air outlets 70 of the first subset of inner projections 60 are arranged to emit air radially outwardly, away from the longitudinal axis C of the diffuser 10. The air outlets 76 of the second subset of inner projections 62 are arranged to emit air radially inwardly, towards the longitudinal axis C of the diffuser 10.

The set of outer projections 64 are arranged in an annular array amongst the second array of air outlets 34, along the raised outer peripheral area 46 of the grille 30. In this embodiment, the set of outer projections 64 comprises ten projections which are equally angularly spaced about the longitudinal axis C. The set of outer projections 64 are arranged such that each of the second subset of inner projections 62 emits air towards a respective one of the set of outer projections 64. Similar to the set of inner projections 60, 62, each of the set of outer projections 64 comprises an air inlet 80 formed in the grille 30, an air outlet 82 and a bore 84 for conveying air from the air inlet 80 to the air outlet 82. The air outlets 82 of the set of outer projections 64 are arranged to emit air towards the central portion 36 of the grille 30, and are preferably arranged to emit air radially inwardly, towards the longitudinal axis C of the diffuser 10 so that each of the set of outer projections 64 emits air towards a respective projection of the set of inner projections 60, 62.

The intermediary set of projections 66 are arranged in an annular array amongst the second array of air outlets 34 of the grille 34. In this embodiment, the intermediary set of projections 66 comprises ten projections which are equally angularly spaced about the longitudinal axis C. The intermediary set of projections 66 are arranged such that each of the intermediary set of projections 66 is angularly offset relative to the set of inner projections 60, 62 and to the set of outer projections 64. Similar to the set of inner projections 60, 62, each of the intermediary projections 66 comprises an air inlet 86 formed in the grille 30, an air outlet 88, and a bore 90 for conveying air from the air inlet 86 to the air outlet 88. The air outlets 88 of the intermediary projections are arranged to emit air towards the central portion 36 of the grille 30, preferably radially inwardly towards the longitudinal axis C of the diffuser 10, so that none of the intermediary projections 66 is located in the path of air emitted from the set of inner projections 60, 62 or the set of outer projections 64.

The airflow dampener 28 is located between the grille 30 and the baffle 16. The airflow dampener 28 is in the form of a circular disc or plate which comprises of a fine mesh texture suitable for airflow reduction. As shown in FIGS. 8 a and 8 b , the periphery of the airflow dampener 28 is supported by a ledge 92 formed on the internal surface of the tapering wall 20 of the baffle 16. The ledge 92 is located generally midway between the air inlet end 14 and the air outlet end 18 of the baffle 16.

As hot air flow passes through the diffuser 10, the temperature of the tapering wall 20 of the baffle 16 will rise. To shield the user from the tapering wall 20 of the baffle 16, the diffuser 10 further comprises an external wall 100 which surrounds the baffle 16 and the grille 30. The external wall 100 is generally frustoconical in shape and has a circular first end 102 and a circular second end 104 which is larger than the first end 102.

The external wall 100 comprises a first set of fastening elements 106 and a second set of fastening elements 108 formed on the internal surface of the external wall 100, and which are connected to the baffle 16 and the grille 30 during assembly of the diffuser 10. The first set of fastening elements 106 are arranged in a circular array and are equally angularly spaced about the longitudinal axis A of the diffuser 10. Furthermore, the first set of fastening elements 106 are located generally midway between the first end 102 and the second end 104 of the external wall 100. The second set of fastening elements 108 are arranged in a circular array and are equally angularly spaced about the longitudinal axis C of the diffuser 10. Furthermore, the second set of fastening elements 108 are located generally midway between the first set of fastening elements 106 and the second end 104 of the external wall 100.

The first set of fastening elements 106 serve as a fastener connecting the baffle 16 to the external wall 100 and as a spacer between the baffle 16 and the external wall 100 defining a second annular air chamber 110 therebetween. The diffuser 10 comprises a plurality of ports which place the annular air chamber 110 in fluid communication with the ambient atmosphere. This can allow warm air to be conveyed out from the annular air chamber 110 during use of the diffuser 10, and allow cool air to enter the annular air chamber 110 following use of the diffuser 10. A first port 112 is located between the first end 102 of the external wall 100 and the air inlet end 14 of the baffle 16. A second port 114 is located between the second end 104 of the external wall 100 and the grille 30.

With reference to FIGS. 6 and 7 , the diffuser 10 further comprises a sealing ring 120 located between the grille 30 and the airflow dampener 28. The sealing ring 120 is in the form of an annular seal comprising at least one guiding means 122. The guiding means 122 provides guidance towards the correct assembly of the sealing ring 120, reducing user error. In a preferred embodiment, there are at least two guiding means 122 along the periphery of the sealing ring 120, spaced apart from each other. The sealing ring 120 is preferably made from silicon rubber and its purpose is to prevent hot air from leaking between the grille 30 and the baffle 16.

With reference to FIG. 7 , the baffle 16 further comprises an RF ID slot 124 located at on the outer surface of the air inlet channel 24, suitable for receiving an RF ID tag 126. The purpose of the RF ID tag 126 is to alert a control circuit of a hair dryer 200 regarding the type of attachment, i.e. diffuser 10, being used. The control circuit of the hair dryer 200 may then adjust relevant settings such as air temperature and airflow rate accordingly.

Each of the components of the diffuser 10 is formed from a plastic material. In this embodiment the components are formed from glass filled nylon.

To assembly the diffuser 10, the airflow dampener 28 is first located within the baffle so that the perimeter of the airflow dampener 28 rests on the ledge 92 of the baffle 16. The airflow dampener 28 comprises at least one guiding aperture 128. Preferably, in this embodiment the airflow dampener 28 comprises three guiding apertures 128. The baffle 16 comprises assembly points 130 corresponding to the guiding aperture 128 positions of the airflow dampener 28. The sealing ring 120 is then located along the air outlet end 18 of the baffle 16. Preferable the internal curvature of the sealing ring 120 corresponds to the peripheral curvature of the air outlet end 18 of the baffle 16, allowing the sealing ring 120 to rest on the baffle 16. The grille 30 is then positioned on the air outlet end 18 of the baffle 16, resting above the sealing ring 120. The outer periphery of the grille 30 further comprises male angular alignment members 132 which are received by the guiding means 122 of the sealing ring 120. The grille further comprises fastening screw receptable 134 along the annular region 40 of the grille 30. Accordingly, the alignment of male angular alignment members 132 of the grille 30 and the guiding means 122 of the sealing ring 120, ensures the alignment of fastening screw receptacle 134 of the grille 30, guiding apertures 128 of the airflow dampener 28 and the assembly points 130 of the baffle 16. Following the placement of the baffle 16, the airflow dampener 28, the sealing ring 120 and the grille 30 on top of each other in accordance with the guiding apertures 128 of the airflow dampener 128, the fastening screws 142 are guided through the assembly points 130 of the baffle 16 and guiding apertures 128 of the airflow dampener 28, and connected to the fastening screw receptacle 134 of the grille 30. This connection of the grille 30 to the baffle 16 also results in the airflow dampener 28 and the sealing ring 120 becoming sandwiched between the baffle and the grille 30 and forming a sub-assembly 136.

The assembly of the diffuser 10 is completed by securing the sub-assembly 136 to the external wall 100 using the first set of fastening elements 106 and the second set of fastening elements 108. A first set of circumferentially spaced mating elements 138 of baffle 16 engage with the first set of fastening elements 106. A second set of circumferentially spaced mating elements 140 of the grille 30 engage with the second set of fastening elements 108.

In use the diffuser 10 is attached to the airflow outlet end 202 of a hair dryer 200. For example the diffuser 10 may be attached to the hair dryer by a magnet 150 located at the air inlet end 14 of the baffle 16. 

1. A diffuser for attachment to an airflow outlet end of a hair dryer, the diffuser comprising: at least one air inlet for receiving an airflow from a hair dryer; a grille comprising a central portion and a plurality of air outlets for emitting a first part of the airflow from the diffuser; and a plurality of projections upstanding from the grille for contacting the hair of a user and for emitting a second part of the airflow, each of the projections comprising a single air outlet; wherein the plurality of projections comprise a set of inner projections arranged about the central portion of the grille, and a set of outer projections arranged about the inner projections, and wherein the air outlets of a first subset of inner projections are arranged to emit air away from the central portion of the grille and the air outlets of a second subset of inner projections are arranged to emit air towards the central portion of the grille, and the air outlets of the outer projections are arranged to emit air towards the central portion of the grille.
 2. The diffuser according to claim 1, wherein the inner projections are arranged in an annular array.
 3. The diffuser according to claim 1, wherein the inner projections are arranged about some of the air outlets of the grille.
 4. The diffuser according to claim 1, wherein the number of projections in the first subset of inner projections is equal to the number of projections in the second subset of inner projections.
 5. The diffuser according to claim 1, wherein the inner projections are arranged at equiangular intervals.
 6. The diffuser according to claim 1, wherein the first subset of inner projections and the second subset of inner projections are alternately arranged about the central portion of the grille.
 7. The diffuser according to claim 1, wherein the air outlets of first subset of inner projections are arranged to emit air radially away from the central portion of the grille and the second subset of inner projections are arranged to emit air radially towards the central portion of the grille.
 8. The diffuser according to claim 1, wherein the outer projections are arranged in an annular array.
 9. The diffuser according to claim 1, wherein the set of inner projections and the set of outer projections are concentric.
 10. The diffuser according to claim 1, wherein the angular spacing between adjacent inner projections is substantially the same as the angular spacing between adjacent outer projections.
 11. The diffuser according to claim 1, wherein the outer projections are arranged at equiangular intervals.
 12. The diffuser according to claim 1, wherein the air outlets of the outer projections are arranged to emit air radially towards the central portion of the grille.
 13. The diffuser according to claim 1, comprising a set of intermediary projections located between the inner projections and the outer projections.
 14. The diffuser according to claim 13, wherein each of the intermediary projections comprises a single air outlet arranged to emit air towards the central portion of the grille.
 15. The diffuser according to claim 14, wherein the air outlets of the intermediary projections are arranged to emit air radially towards the central portion of the grille.
 16. The diffuser according to claim 13, wherein the intermediary projections are angularly offset relative to both the inner projections and the outer projections.
 17. The diffuser according to claim 13, wherein the intermediary projections are arranged in an annular array.
 18. The diffuser according to claim 13, wherein the number of intermediary projections is equal to the number of outer projections.
 19. The diffuser according to claim 1, wherein the outer projections are located adjacent to the outer periphery of the diffuser.
 20. The diffuser according to claim 1, wherein the central portion of the grille comprises a circular unperforated grille area. 